This may give you an idea. This assumes that you want to break on spaces only, add comma,period or other possible break characters to the second parameter of FINDC. This also assumes that you aren't likely to have any single word longer than 20 characters.

data example;
x= "This is a really long string that I want to split into two strings of less than 200 characters. The current length is going to be a randome collection of words untill I get something long enough to split. Of course we may have some issues with how the long the longest individula word may be in the source string but that's life.";
length string1 string2 $ 200;
if length(x) < 200 then String1=X;
Else do;
string1 = substr(x,1,findc(x,' ',180));
string2 = substr(x,findc(x,' ',180));
end;
run;